The present invention relates to a cylinder for escapement to perform a stable operation.
An escapement cylinder, in which two piston rods of two cylinders mounted in parallel on a cylinder body are alternately moved backward and forward by the action of a pressured fluid and other piston rod is brought in backward when one piston rod attains a vicinity of a forwarding edge, has been known conventionally (for example, see Japanese Utility Model Publication No. 2514783). According to this known escapement cylinder, a communication path mounted between both cylinders introduces the pressured fluid used for making a first piston rod forward into a pressured chamber at the side at which the piston rod is made backward in other cylinder when the first piston rod attains the forward edge and the piston rod is brought in backward with that pressured fluid.
According to the escapement cylinder with the above constitution, as described above, it is possible to perform a desired operation such that switching the pressured fluid appropriately in the above communication path makes the other piston rod when one piston rod attains a vicinity of the forwarding edge. However, when one piston rod attains a vicinity of the forward edge, a part of the pressured fluid for making the piston rod forward is introduced in the other cylinder. Therefore, the escapement cylinder with the above constitution involves a problem such that the fluid pressure at the side for making the piston rod forward is lowered temporarily at this time and the thrust of the piston rod is lowered.
Further, during one piston rod is making forward, the fluid pressure is not effected on the piston rod of the other cylinder. Accordingly, when the external force is effected on this piston rod, there is a problem such that the piston rod is moved by this external force.
In order to solve the forgoing problems, for example, Japanese Laid Open Patent Publication No. 11-82420 discloses an escapement cylinder such that other piston rod is brought in locked automatically during one piston rod is moving forward and backward. However, in this well known example, when one piston rod is making forward, the fluid pressure for driving effects on other piston rod which is locked on the forwarding edge in the direction for making the other piston rod backward. Therefore, there is a case that the force effects on the other piston rod in the direction orthogonal to an axial line through a locking mechanism from this locked piston rod to have effect on the operation of the piston rod in forward movement. As a result, a countermeasure is required to solve this problem. Further, it is desired that the above described locking mechanism has a simple constitution and is stably operated.
The present invention has been made taking the foregoing problems into consideration, a technical object of which is to provide an escapement cylinder having a simple constitution and operating stably.
A further concrete technical object of the present invention is to provide an escapement cylinder such that when a piston rod attains a vicinity of the forward edge, the thrust of the piston rod is not lowered temporally by lowering of the fluid pressure and the other piston rod is not moved by the external force during one piston rod is moving.
Another technical object of the present invention is to provide an escapement cylinder such that the force does not effect on the other piston rod in the direction orthogonal to an axial line through a locking mechanism from this locked piston rod differently from the escapement cylinder disclosed in the above described Japanese Laid Open Patent Publication No. 11-82420 when the other piston rod is automatically locked during one piston rod is moving. Accordingly, this escapement cylinder has a locking mechanism, which stably operates with a very simple constitution.
In order to solve the foregoing problems, an escapement cylinder according to the present invention comprises two pistons arranged in parallel within one cylinder body, two piston rods, which are extended in parallel from the two pistons, of which front edges are projected to the outside and which has hollows for locking therein, head side pressured chambers and rod side pressured chambers, which are comparted and formed on opposite sides of the respective pistons, respectively, ports for supplying a pressured fluid separately to the two head side pressured chambers, two communicating paths for communicating the head side pressured chamber of one piston with the rod side pressured chamber of other piston when one piston moves to a forward edge by supply of the pressured fluid to the head side pressured chamber and a rod holding unit plate, which is supported by a pin between the two piston rods oscillatably and has engaging units at portions facing to respective piston rods, respectively, to operate such that one engaging unit is in sliding contact with a side surface of this piston rod and the oscillation of this piston rod is regulated during one piston rod is making forward or is setting back and at the same time, other engaging unit is engaged in a hollow of other piston rod located at the forward edge to regulate the returning operation of the other piston rod.
According to an embodiment of the present invention, the rod holding unit plate is formed by a triangle plate, the engaging units are formed by two vertical angles and the pin is mounted between these vertical angles.
According to another embodiment of the present invention, the respective piston rods comprise a first portion at a base edge along the piston and a second portion at a front edge, which is coupled with the front edge of this first portion and is in sliding contact with the rod holding unit plate. The outer size of this second portion is made larger than the outer size of the first portion, so that the hollow is formed on the coupling portion of these both portions by the difference in size between these two portions.
Said first portion of the respective piston rods forms a column shape and the second portion of the respective piston rods forms a rectangular column shape. It is preferable that engaging a projection in T-shape, which is formed on the front edge of the first portion, in a T-shaped groove, which is formed on the base edge of the second portion, allows these first and second portions to be coupled each other in floating.
The escapement cylinder having above descried constitution operates two piston rods alternately by supplying a pressured fluid and automatically locks other piston rod to a forwarding edge with a rod holding unit plate during one piston rod is making forward or making backward. For example, in the state that a second piston rod is mounted at the forwarding edge and a first piston rod is mounted at a backward edge, supplying the pressured fluid to a pressure chamber at a head side of the first piston allows this first piston rod to make forward. At this time, in the above rod holding unit plate, one holding unit is in sliding contact with the side surface of the first piston rod in moving and the oscillation thereof is regulated. On the other hand, in the above rod holding unit plate, other holding unit is fitted and engaged in a hollow of the second piston rod, which is located at the forwarding edge and the returning operation thereof is limited.
When he foregoing first piston rod attains the forward edge, the head side pressure chamber of this first piston and the rod side pressure chamber of the second piston are communicated each other in the communicating path, so that the pressured fluid is flowed into this rod side pressure chamber and the foregoing second piston rod begins to make backward from the forward edge. At this time, in the forgoing rod holding unit plate, two holding units are fitted into hollows in the first and the second piston rods at the forwarding edge at the same time, respectively, to be capable of being oscillated when the foregoing first piston rod attains the forwarding edge. Therefore, the foregoing second piston rod is unlocked temporarily to be capable of making backward. Then, when this second piston rod starts making backward, in the foregoing rod holding unit plate, one engaging unit is in sliding contact with the side surface of the second piston rod to regulate its oscillation. On the other hand, other engaging unit is engaged in the hollow of the foregoing first piston rod located at the forwarding edge to regulate its returning operation.
In the case that the foregoing second piston rod, which attains the backward edge, the same operation as that of the above described case is performed.
Thus, the piston rod attaining the forward edge is locked there, so that the thrust of the piston rod is not lowered temporally by lowering of the fluid pressure and the other piston rod is not moved by the external force during one piston rod is moving differently from the conventional escaping cylinder.
Further, when one piston rod is locked at the forwarding edge, the fluid pressure does not effect this piston rod unless other piston rod attains the forwarding edge. Therefore, the force is not applied to the side surface of the piston rod in forward movement by pushing the rod holding unit plate with this locked piston rod. Thus, respective piston rods are capable of operating stably despite of a very simple constitution of the locking mechanism.